Your Fitness Tracker May Be Overestimating Your Calorie Burn By 23%

The claim: If you think your wearable fitness tracker is giving you a totally spot-on measurement of how many calories you burn throughout the day, you might be surprised. According to a study published in Medicine & Science in Sports & Exercise, the accuracy of these activity monitors varies widely.

The research: Researchers from Iowa State University compared the accuracy of 8 consumer fitness trackers against lab equipment that also measures energy expenditure. They had 60 subjects (30 men and 30 women) wear all 8 trackers plus the lab model while they did a series of 13 everyday activities (from typing at a computer to running) for 69 minutes total. The results? The BodyMedia FIT did the best compared to the lab equipment, with a 9.3% error rating, which, the researchers say, is comparable to research models. Here’s how the rest fared: Fitbit Zip (10.1%), Fitbit One (10.4%), Jawbone Up (12.2%), Actigraph (12.6%), Directlife (12.8%), Nike Fuel Band (13%) and Basis Band (23.5%).

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What it means: Not all trackers are made equal. Depending on the one you use, you may not be getting the most accurate picture of your daily calorie burn.

The bottom line: Sure, your tracker may not be able to pinpoint your energy expenditure down to the calorie, but that doesn’t make it useless. These devices can be great motivational tools, and can, at the very least, give you an estimate of how active you are (research shows that adults tend to overestimate their activity levels). The jury is still out on whether fitness trackers lead to long term improvements in activity levels, but if you feel that using one makes you more likely to get up and get moving, by all means, start tracking. Just make sure you do your research on the device before you shell out the cash.